Nodes of parallel computing systems are connected by an interconnect subsystem comprising a network and network interface components. In case the parallel processing elements are located in nodes (in some cases referred to as computing blades) the blades contain a network interface card (in some cases the interface is not on a separate card). An operating system is chosen in part based on the characteristics of the network. Network Interface Controllers (NICs) are designed to attain the best possible performance given the characteristics of the processors, the processor interface protocol, the network, and the operating system.